Fluid compressor system

ABSTRACT

A system for compressing a fluid, such as ethylene monomer and adding a constituent to same to produce a product therefrom, for instance: a polymerized product, such as polyethylene. The system sets forth the use of plural stages of centrifugal compressors requiring a given amount of horsepower for the driving thereof, and only some of the required horsepower is externally supplied. Some of the energy stored in the fluid, through the compressing thereof and the introduction of heat thereto, is deployed in the system to drive some of the compressor stages.

United States Patent Hornschuch [45] Mar. 14, 1972 [54] FLUID COMPRESSOR SYSTEM 3,257,806 6/1966 Stahl ..60/38 X [72] Inventor: Balms Hornschuch Easmn, Pa. 3,441,393 4/1969 Fmneran et al ..48/196 X [73] Assignee: Ingersoll-Rand Company, New York, NY. Primary Examiner-Joseph Scovronek [22] Filed: Sept 25, 1969 Attorney-Carl R. Horten, David W. Tibbott and Bernard J.

Murphy [21] Appl. No.: 861,026

[57] ABSTRACT [52] US. Cl ..23/260, 23/288 E, 23/289, A system for compressing a fluid, such as ethylene monomer 417/377 and adding a constituent to same to produce a product [51] Int. Cl. ..B01J l/00,C08d 3/08, FOlk 25/02 therefrom, f instance; a po|ymerized product, Such as [58] Field of Search ..23/289, 288 E, 284, 260, 285; Polyethylene The system sets forth the use f plural stages f 260/94.9 P, 60/37, 417/377; 48/196 centrifugal compressors requiring a given amount of horsepower for the driving thereof, and only some of the required [56] References Cited horsepower is externally supplied. Some of the energy stored UNITED STATES PATENTS in the fluid, through the compressing thereof and the introductron of heat thereto, is deployed in the system to drive some of AUSUH, Jr. the compressor stages 3,023,202 2/1962 Schappert ..23/289 X 3,10l,592 8/1963 Robertson et al ..60/37 X 5 Claims, 5 Drawing Figures 44 42 REACTOR IO 40 6 4 24 22 0 7 7 1 48 4s 7 e L L i i l i 50 52 68-4 I 66 62 w 9 54 l 64 24 r 22 0 Tea o l y 62 58 38 it M 22 56 TY M SEPARATOR 64 66 62 0 J i? 34 22 so Y i 66 24 36 0 34 M I 32 2a 30 r o o FLUID COMPRESSOR SYSTEM This invention pertains to fluid compressor systems, and in particular to high pressure fluid compression systems used to effect the production of a product, such as the systems used primarily in the chemical industry. By way of example, reference is made to gas compression systems, to wit: those concerned with the compression of ethylene monomer, for instance, to pressures in the range of 20,000 to 75,000 p.s.i., where only a small part of the compressed fluidor as in the example, the gas: ethylene monomer-will be turned into a product, degassed polymer, and a larger part of the gas volume will be recycled.

Presently, compression systems of this character use reciprocating compressor equipment. Such equipment is extremely bulky, operates at very low speeds, consumes much floor space and requires a great deal of maintenance. As plant capacities become larger, reciprocating machines will have to be used in multiple; this is so because present technology suggests that it is impractical to build larger volume machines, due to the extremely high bearing loads to which these machines are subjected. Machines of some other type are more practical and attractive from space, maintenance, and cost standpoints.

Known systems require given amounts of horsepower and, of course, derive all such power from sources external of the system. It is not known to recover power from within the system, yet such recovery should afford significant economies.

It is an object of this invention, then, to teach a fluid compressor system comprising a plurality of powered means for compressing fluid to efiect the production of a product; means for admitting fluid and at least one constituent to said system; reactor means, coupled to said compressing means, for receiving the compressed fluid and constituent and for causing a reaction to occur between said one constituent and fluid to initiate formation of the product from a portion of the fluid; separator means for separating the product from the remaining fluid; and means communicating said separator means with said reactor means for conducting the fluid and said constituent therebetween; said communicating means including means using a portion of the energy stored in said compressed fluid for powering given means of said plurality.

A feature of this invention comprises the provisioning of several stages of centrifugal fluid compressors of compressing the fluid to effect the production of a product, directing the compressed fluid and constituent to a reactor in which there is caused to occur a reaction between the constituent and the fluid to initiate formation of the product from a portion of the fluid, and separating the product from said portion of the fluid, in which the invention teaches the conduction of the fluid to the driving means provisioned for some of the compressor stages; thus, energy inhering in the compressed fluid is used, i.e., recovered, in the system.

Further objects and features of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying figures in which:

FIG. 1 is a schematic diagram of a first or preferred embodiment of the invention; and

FIGS. 2 through 5 are schematic diagrams of alternate embodiments of the invention in which differing arrangements for powering the low-pressure compressor stages are shown.

As shown in FIG. I, the system comprises a plurality of turbine-compressor modules 12, 14, l6, l8 and 20. Modules 12, I4, and 16 comprise the low pressure modules of the system, and modules 18 and 20 comprise the high pressure components of the system. Each of the modules includes a turbine unit 22 which drives a compressor unit 24.

As noted earlier, the invention broadly comprises a fluid compressor system, used to produce a product through the compressing of the fluid. By way of example only the following discussion discloses the invention in connection with the compression of a gas, ethylene monomer, toward the production of a degassed polymer: polyethylene. It will be understood, however, that the teaching herein can be used for the compression of other fluids.

An inlet feed stock line 26 provides means for admitting the gas to the system. The gas is fed to a pump 28 which is driven by a motor 30. The gas proceeds through an inlet line 32 to a recycling line 34.

The gas is conducted, via line 34, through a heat exchanger 36 and proceeds therefrom to modules l2, 14, 16, 18 and 20, serially, for successively increased compression. Between modules 14 and 16 is disposed an intercooler 38. The intercooler is provided to bring the initially compressed gas down to acceptable temperature parameters for further subsequent compression. The finally highly compressed gas leaves module 20 and proceeds by way of high-pressure line 40 to a reactor 42. In this embodiment, reactor 42 comprises an autoclave device. Accordingly, in reactor 42 the compressed gas has heat energy added thereto together with a catalyst, the latter comprising some given constituent, thus there is initiated a formation of the product; the constituent is supplied to the reactor by way of line 44. However, as shown in the embodiments depicted in FIGS. 2, 3 and 4, the catalyst agent or constituent can be admitted to the system elsewhere then through the reactor.

The constituent and gas mixture proceeds through a dump valve 46 which is provisioned for safety purposes only. Valve 46 contemplates a device automatically responsive to an unfavorable reaction between the gas and catalytic constituent quickly to disgorge the contents of the reactor, so as to avoid damaging the system.

The gas and constituent mixture comprises molten polymer. The molten polymer is conducted through line 48 at very high pressure and velocity to turbines 22 of modules 20 and I8, serially. The energy inhering in the molten polymer drives the turbines 22 which in turn drive the compressor units 24 associated therewith. Accordingly, energy put into the product gas is recovered, in part, through the teaching of this system. From turbine 22 of module 18 the molten polymer is conducted through a back pressure valve 50 by way of separator supply line 52 to an expansion valve 54.

In the prior art it is the teaching to conduct the gas from the reactor directly to an expansion valve to expand the gas to a optimum pressure for the separation of the product therefrom. This prior practice neglected to take advantage of the power recovery taught by the instant invention. The expansion valve 54 incorporated in this disclosed system is provided for the same known purpose: to bring the gas and constituent mixture down to the proper pressure level for product separation. Thereafter the gas and the constituent mixture is conducted to a separator 56 which has a product out" line 58, from which product issues, and the separator 56 is throughconnected with recycling line 34 to recycle the nonproduct-forming gas, i.e., unreacted ethylene monomer, back into the system.

Turbines 22 of modules l2, l4 and 16 are driven by external power. Therefore, steam supply lines 60 and steam return lines 62 are throughconnected with each of these turbines. High-pressure and low-pressure gas leakage paths or lines 64 and 66, respectively, provide for the return of any leakage back into the system. Lines 64 and 66 are through-connected with high-pressure intercoupling path or line 68 and low-pressure intercoupling path or line 70.

Lines or paths 64, 66, 68 and 70 are so-called because the invention contemplates the encasing of the compressor stages and the turbine drivers in a common housing structure. Thus, leakage paths" will be provisioned downstream, within such a housing, for the reinjection of leakage gas.

About 50 percent of the energy required for driving the compressor units is furnished by the recycled gas, with the teaching of my invention. The remaining portion of power is supplied from sources outside of the system, i.e., steam supplied via lines 60.

FIG. 1 teaches the use of externally derived steam for powering the low-pressure modules l2, l4 and 16. In FIGS. 2 through 5 are set forth alternate embodiments of the novel system in which other means for powering the low-pressure compressor stages are shown. Index numbers given in FIGS. 2

through which are the same as, or similar to, index numbers in FIG. 1 denote same or similar components.

FIG. 2 shows a first alternate system arrangement using but two turbine-compressor modules. In this the ethylene monomer is supplied via inlet feed stock line 26 at a pressure level of approximately 3,000 lbs. and enters a turbocompressor 80. The catalyst or constituent feed line 44, in this embodiment, admits the agent to the lowpressure compressor 24 of turbocompressor 80. The pressure of the gas leaving turbocompressor 80 is in the neighborhood of 13 to 15,000 p.s.i. The gas is cooled in intercooler 82; it might be noted here that it is necessary to cool ethylene monomer whenever it reaches a given, upper, critical level determined by the polymerization temperature limit of the gas. After the cooler 82 the gas enters another turbocompressor 84 which compresses to the final system pressure. This turbo compressor 84 is driven by the expansion of the molten polymer proceeding from a reactor 42' similar to the reactor 42 of FIG. I.

In the FIG. 2 embodiment, the same gas, ethylene monomer, supplies the power for the low-pressure turbocompressor 80. An ethylene source line 86 supplies the gas, at atmospheric pressure, to a motorized reciprocating compressor 88. From compressor 88 the gas proceeds to a motorized centrifugal compressor 90 and from there to a closed, fueled heater 92. The heated, compressed gas is admitted to turbine 22 of turbocompressor 80 to effect the driving thereof. The expanded gas is returned to the compressor 90 by way of a cooler 94; it is recycled into compressor 90 together with a given quantity of makeup gas supplied via line 86 and compressor 88.

FIG. 3 sets forth a system where again the driving force for a low pressure turbocompressor 80 is derived from the ethylene. The ethylene in this embodiment, is handled in a more closed" cycle. Of course, the low pressure and high pressure values for this closed ethylene cycle will vary considerably with the power requirements of the compressor. The ethylene is compressed by a compressor 90 driven by an electric motor. It is then heated in a closed, fueled heater 92, enters the turbine 22 of turbocompressor 80, and is expanded to some given low pressure, and cooled, in cooler 94, before it reenters the compressor 90. A makeup compressor 88 keeps the ethylene cycle charged at its proper pressure level, and is supplied by a source line 86' throughconnected with an inlet feed stock line 26.

FIG. 4 discloses a system based on utilizing an air-gas turbine cycle. Again, this is a closed cycle where the air is compressed by a motor driven compressor 90, then heated in a closed, fueled heater 92, introduced into the turbine 22 of a turbocompressor 80', expanded to the low pressure end of the cycle and it reenters compressor 90, after it has been cooled in cooler 94. A makeup air compressor 88 is provisioned to keep the system charged.

As the media in the low-pressure ethylene compressor unit 24 and the turbine 22, of compressor 80', differ, sealing (not shown) therebetween is provided and leakage which occurs on the ethylene side is recompressed to enter the system at the feed stock pressure level. This system, then, also incorporates a seal leak compressor 100, motor driven, for compression and reinsertion of the leakage gas. Constituent feed line 44, in this embodiment, admits the catalytic agent or constituent to the high-pressure turbocompressor 84.

FIG. 5 illustrates an embodiment of the system in which a steam cycle is used for driving the turbine 22 of the low-pressure compressor 80'. Steam is generated in a boiler 102, introduced into the turbine 22 of compressor 80' where it is expanded to a lower pressure level; then the remaining energy of the steam is used to drive a steam turbine 104 which in turn drives the feed stock compressor 96. This steam turbine 104, in cooperation with an interposed condenser 106, condenses the steam, and the condensate reenters the steam boiler. In this system also, provision is made to recompress the ethylene leakage of the low pressure ethylene compressor, seal leak compressor 100 being provisioned for this purpose.

Each of the novel systems of FIGS. 1 through 5 as a principal object thereof the powering of given ones of the plurality of compressing means with the energy stored in the compressed fluid.

The capabilities of, and requirements for, each system embodiment will vary, one from the other. Even so, each system clearly requires empowering by some Y" horsepower, and my method teaches the supply of less than "Y horsepower (i.e., Y-A horsepower) thereto from sources external of the system, and the supply of the remaining requisite horsepower (i.e., A" horsepower) from a source internal of the system. Specific parameterspressures, temperatures, flow volumes, etc.,per system could be presented, but they would not lend any emphasis to the teaching of a novel power recovery which so clearly proceeds from this disclosure.

By way of the catalytic-constituent supply lines 44 (FIGS. 1-5 some given constituentsome one or more-is added to the finally, fully compressed fluid (ethylene monomer). The constituent will or may constitute a source of free radicals, to wit: oxygen, an organic peroxide, or the like. The particular catalyst is not material to the principal objects of this invention. As for the reactors incorporated in the several systems, they shall comprise means for causing a reaction to occur between the fluid and catalytic constituent, to initiate formation of the product, for example: means for imparting heat energy to the compressed fluid and constituent. Also, to be specific, the compressor units 24 set forth in the preferred system embodiment of FIG. 1 each comprise two centrifugal stages. But this is'a particular configuration derived from an analysis of given and desired system parameters. Those skilled in the art to which this invention pertains will find alterations and modifications of the several systems are possible as they apply ordinary engineering skill and devise differing configurations while proceeding from the teaching of my invention.

While I have described my novel system, in connection with specific embodiments thereof, it is to be clearly understood, therefore, that this is done only by way of example and not as a limitation to the scope of my invention as set forth in the ob- 40 jects thereof, at least.

I claim:

1. A fluid compressor system, for polymerizing ethylene,

comprising:

a plurality of centrifugal compressor stage means for compressing ethylene monomer to effect the production of product polyethylene therefrom;

power means drivingly coupled to at least one of said compressor stage means for effecting operation thereof;

fluid-admitting means for admitting ethylene monomer to said plurality of stage means;

catalyst-admitting means for admitting at least one catalytic constituent to said system;

reactor means, directly coupled to said compressor stage means, for receiving the compressed ethylene monomer and constituent and for causing a reaction to occur between said constituent and said ethylene monomer to initiate formation of the product polyethylene from a portion of the ethylene monomer;

separator means for separating the product polyethylene from the remaining portion of the ethylene monomer;

a line for conducting reacting constituent and ethylene monomer therethrough, said line communicating said separator means with said reactor means; and

recovery turbine stage means interposed in said line, and directly and drivingly coupled to at least a given compres sor stage means, of said plurality thereof, other than said at least one stage means, said turbine stage means being operative, in response to a throughconduct of said reacting constituent and ethylene monomer, through the influence of a portion of the energy stored in the reacting constituent and ethylene monomer, for powering said given compressor stage means.

2. A fluid compressor system, according to claim 1,

wherein:

said ethylene monomer and recycling said ethylene monomer for repetitive compressing, heating and cooling thereof, said gas turbine being disposed for expanding said ethylene monomer following the heating thereof.

5, A fluid compressor system, according to claim 2,

wherein:

said power means comprises steam-generating means, said steam-generating means including a fueled steam boiler, steam expander means, and a condenser, all serially throughconnected for recycling of steam through said system.

l t t 

2. A fluid compressor system, according to claim 1, wherein: said plurality of compressor stage means comprises serially coupled stages of centrifugal compressors.
 3. A fluid compressor system, according to claim 2, further including: means for conducting leakage ethylene monomer from said plurality of compressor stage means to said fluid-admitting means.
 4. A fluid compressor system, according to claim 2, wherein: said power means comprises a gas turbine, means for admitting ethylene monomer to said gas turbine, and further comprises means for compressing, heating and cooling said ethylene monomer and recycling said ethylene monomer for repetitive compressing, heating and cooling thereof, said gas turbine being disposed for expanding said ethylene monomer following the heating thereof.
 5. A fluid compressor system, according to claim 2, wherein: said power means comprises steam-generating means, said steam-generating means including a fueled steam boiler, steam expander means, and a condenser, all serially throughconnected for recycling of steam through said system. 